Sarcoidosis is a disease characterized by the growth of tiny collections of inflammatory cells (granulomas) in any part of your body — most commonly the lungs and lymph nodes. But it can also affect the eyes, skin, heart, and other organs.

The cause of sarcoidosis is unknown, but experts think it results from the body’s immune system responding to an unknown substance. Some research suggests that infectious agents, chemicals, dust, and a potential abnormal reaction to the body’s proteins (self-proteins) could be responsible for the formation of granulomas in genetically predisposed people.